Here we propose Achilles, a web-based application which provides an easy-to-use interface to explore the mobility fluxes and the connectivity of urban zones in a city, as well as to visualizes changes in the transport system resulting from the addition or removal of transport modes, urban zones and single stops. Achilles is based on a multiplex network representation of mobility data [1]}, where every layer describes people's movements with a given transport mode, e.g. buses, metros, taxis. A node in a layer represents an urban zone of the city, edges indicate routes between zones and edge weights indicate the amount of people moving between two nodes in a given time window. Achilles exploits this network representation and allows the user to visualize changes in the transport system resulting from the addition or removal of transport modes, urban zones and single stops. Notably, Achilles allows to compute the Heel-ness of a zone, a measure introduced in this paper which indicates the probability of a zone to disconnect the network when edges adjacent to it are removed. The computation of the Heel-ness allows Achilles to state that the transport system has an Urban Achilles Heel if there is at least one urban zone with a non-zero Heel-ness.
